U.S. patent number 7,677,602 [Application Number 11/928,136] was granted by the patent office on 2010-03-16 for tube fitting.
This patent grant is currently assigned to Swagelok Company. Invention is credited to Mark A. Bennett, Peter C. Williams.
United States Patent |
7,677,602 |
Bennett , et al. |
March 16, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
Tube fitting
Abstract
A tube fitting for a tube end has a first coupling member and a
second coupling member joined with the first coupling member. A
tube gripping device is disposed between the first coupling member
and the second coupling member such that assembly of the first
coupling member with said second coupling member to a pulled-up
condition causes the tube gripping device to be plastically
deformed and swaged into the tube to grip and seal the tube. The
first coupling member engages an internal surface of the second
coupling member to provide an indication of completed pull-up.
Inventors: |
Bennett; Mark A. (Bainbridge
Township, OH), Williams; Peter C. (Cleveland Heights,
OH) |
Assignee: |
Swagelok Company (Solon,
OH)
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Family
ID: |
37617622 |
Appl.
No.: |
11/928,136 |
Filed: |
October 30, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080061549 A1 |
Mar 13, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11522814 |
Sep 14, 2006 |
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10467444 |
Sep 19, 2003 |
7108228 |
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PCT/US02/03431 |
Feb 6, 2002 |
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60266735 |
Feb 6, 2001 |
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60329943 |
Oct 17, 2001 |
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Current U.S.
Class: |
285/3; 285/389;
285/323; 285/249 |
Current CPC
Class: |
F16L
19/14 (20130101); F16L 19/10 (20130101) |
Current International
Class: |
F16L
35/00 (20060101) |
Field of
Search: |
;285/3,323,249,245,255,257,247,248,4,342,343,332,389 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
387081 |
|
Nov 1988 |
|
AT |
|
556445 |
|
Feb 1960 |
|
BE |
|
4041679 |
|
Jun 1992 |
|
DE |
|
10206684 |
|
Aug 2003 |
|
DE |
|
1057900 |
|
Feb 1967 |
|
EP |
|
034 493 |
|
Aug 1981 |
|
EP |
|
118 656 |
|
Jun 1986 |
|
EP |
|
205 170 |
|
Dec 1986 |
|
EP |
|
224 188 |
|
Jun 1987 |
|
EP |
|
286568 |
|
Dec 1988 |
|
EP |
|
309 179 |
|
Mar 1989 |
|
EP |
|
371 063 |
|
Feb 1992 |
|
EP |
|
484 091 |
|
May 1992 |
|
EP |
|
285 677 |
|
Dec 1992 |
|
EP |
|
396 367 |
|
Jan 1993 |
|
EP |
|
531 068 |
|
Mar 1993 |
|
EP |
|
581 408 |
|
Feb 1994 |
|
EP |
|
528 079 |
|
Mar 1994 |
|
EP |
|
489 289 |
|
May 1994 |
|
EP |
|
638 752 |
|
Feb 1995 |
|
EP |
|
523 020 |
|
Feb 1996 |
|
EP |
|
583 707 |
|
Mar 1996 |
|
EP |
|
441 676 |
|
Jun 1996 |
|
EP |
|
751 334 |
|
Jan 1997 |
|
EP |
|
762 003 |
|
Mar 1997 |
|
EP |
|
863 354 |
|
Sep 1998 |
|
EP |
|
879 980 |
|
Nov 1998 |
|
EP |
|
895 014 |
|
Feb 1999 |
|
EP |
|
940 617 |
|
Sep 1999 |
|
EP |
|
1020675 |
|
Jul 2000 |
|
EP |
|
1033518 |
|
Sep 2000 |
|
EP |
|
1055859 |
|
Nov 2000 |
|
EP |
|
1647752 |
|
Apr 2006 |
|
EP |
|
818587 |
|
Mar 1937 |
|
FR |
|
1263685 |
|
Jun 1961 |
|
FR |
|
1525750 |
|
May 1968 |
|
FR |
|
981709 |
|
Jan 1965 |
|
GB |
|
2032555 |
|
May 1980 |
|
GB |
|
2080900 |
|
Feb 1982 |
|
GB |
|
2258897 |
|
Feb 1993 |
|
GB |
|
2259123 |
|
Jul 1995 |
|
GB |
|
4429659 |
|
Dec 1969 |
|
JP |
|
461 462 |
|
Jan 1971 |
|
JP |
|
4874317 |
|
Sep 1973 |
|
JP |
|
50149910 |
|
Dec 1975 |
|
JP |
|
513 917 |
|
Jan 1976 |
|
JP |
|
51017219 |
|
Feb 1976 |
|
JP |
|
55159392 |
|
Dec 1980 |
|
JP |
|
55181082 |
|
Dec 1980 |
|
JP |
|
5621679 |
|
Feb 1981 |
|
JP |
|
56066586 |
|
Jun 1981 |
|
JP |
|
56124787 |
|
Sep 1981 |
|
JP |
|
57202084 |
|
Dec 1982 |
|
JP |
|
59006488 |
|
Jan 1984 |
|
JP |
|
59-187184 |
|
Oct 1984 |
|
JP |
|
60139988 |
|
Jul 1985 |
|
JP |
|
6112886 |
|
May 1986 |
|
JP |
|
61099790 |
|
May 1986 |
|
JP |
|
61105391 |
|
May 1986 |
|
JP |
|
5712887 |
|
Jan 1987 |
|
JP |
|
1-58888 |
|
Sep 1987 |
|
JP |
|
63231086 |
|
Sep 1988 |
|
JP |
|
01-058888 |
|
Apr 1989 |
|
JP |
|
1054599 |
|
Nov 1989 |
|
JP |
|
369026 |
|
Oct 1991 |
|
JP |
|
3288091 |
|
Dec 1991 |
|
JP |
|
4023157 |
|
Apr 1992 |
|
JP |
|
4069488 |
|
Mar 1994 |
|
JP |
|
6174171 |
|
Jun 1994 |
|
JP |
|
7-243564 |
|
Sep 1995 |
|
JP |
|
7243564 |
|
Sep 1995 |
|
JP |
|
08-014449 |
|
Jan 1996 |
|
JP |
|
11201347 |
|
Jul 1999 |
|
JP |
|
11325342 |
|
Nov 1999 |
|
JP |
|
2000097377 |
|
Apr 2000 |
|
JP |
|
2000110975 |
|
Apr 2000 |
|
JP |
|
U3069026 |
|
May 2000 |
|
JP |
|
2000170966 |
|
Jun 2000 |
|
JP |
|
200199360 |
|
Apr 2001 |
|
JP |
|
20010099337 |
|
Apr 2001 |
|
JP |
|
2001141169 |
|
May 2001 |
|
JP |
|
19920008397 |
|
May 1992 |
|
KR |
|
19930006359 |
|
Apr 1993 |
|
KR |
|
20010006382 |
|
Jan 2001 |
|
KR |
|
200239292 |
|
Jul 2001 |
|
KR |
|
WO 93/24780 |
|
Dec 1983 |
|
WO |
|
WO 93/25837 |
|
Dec 1983 |
|
WO |
|
WO 84/00796 |
|
Mar 1984 |
|
WO |
|
WO 88/04385 |
|
Jun 1988 |
|
WO |
|
WO 89/09904 |
|
Oct 1989 |
|
WO |
|
WO 89/12190 |
|
Dec 1989 |
|
WO |
|
WO 94/23234 |
|
Oct 1994 |
|
WO |
|
WO 97/07356 |
|
Feb 1997 |
|
WO |
|
WO 97/14905 |
|
Apr 1997 |
|
WO |
|
WO 97/43571 |
|
Nov 1997 |
|
WO |
|
WO 98/32999 |
|
Jul 1998 |
|
WO |
|
WO 98/46925 |
|
Oct 1998 |
|
WO |
|
WO 99/24750 |
|
May 1999 |
|
WO |
|
WO 99/34142 |
|
Jul 1999 |
|
WO |
|
WO 01/20214 |
|
Mar 2001 |
|
WO |
|
WO 01/73333 |
|
Oct 2001 |
|
WO |
|
WO 02/063194 |
|
Aug 2002 |
|
WO |
|
WO 02/063195 |
|
Aug 2002 |
|
WO |
|
2004/013527 |
|
Feb 2004 |
|
WO |
|
WO 2005/019717 |
|
Mar 2005 |
|
WO |
|
2005/106310 |
|
Nov 2005 |
|
WO |
|
2006/088668 |
|
Aug 2006 |
|
WO |
|
2007/002576 |
|
Jan 2007 |
|
WO |
|
2007/048021 |
|
Apr 2007 |
|
WO |
|
2008/030375 |
|
Mar 2008 |
|
WO |
|
2008/057983 |
|
May 2008 |
|
WO |
|
Other References
Notice of Allowance from U.S. Appl. No. 10/467,444, mailed May 5,
2006. cited by other .
Office action from U.S. Appl. No. 10/467,444, mailed Nov. 29, 2005.
cited by other .
Office action from U.S. Appl. No. 10/467,444, mailed May 11, 2005.
cited by other .
Office action from U.S. Appl. No. 10/467,444, mailed Oct. 27, 2004.
cited by other .
Interview Summary from U.S. Appl. No. 10/642,094, mailed Apr. 25,
2006. cited by other .
Supplemental Notice of Allowability from U.S. Appl. No. 10/642,094,
mailed Feb. 28, 2006. cited by other .
Notice of Allowance from U.S. Appl. No. 10/642,094, mailed Jan. 26,
2006. cited by other .
Office action from U.S. Appl. No. 10/642,094, mailed May 11, 2005.
cited by other .
Advisory Action from U.S. Appl. No. 10/642,094, mailed Mar. 22,
2005. cited by other .
Office action from U.S. Appl. No. 10/642,094, mailed Dec. 28, 2004.
cited by other .
Office action from U.S. Appl. No. 10/642,094, mailed Jun. 3, 2004.
cited by other .
Office action from U.S. Appl. No. 11/522,814, mailed Jun. 6, 2007.
cited by other .
Office action from U.S. Appl. No. 11/522,814, mailed Dec. 28, 2007.
cited by other .
Examination Report issued Aug. 22, 2005 from corresponding European
Patent Application Serial No. 02703345.5, 2 pgs. cited by other
.
International Search Report from PCT/US02/03430, mailed Nov. 06,
2002. cited by other .
International Search Report and Written Opinion from
PCT/US2004/026096, mailed Dec. 29, 2004. cited by other .
Parker Hannifin Corporation, Suparcase, The Invisible Breakthrough,
Parker Suparcase Promotion Folder, Parker Hannifin Corporation,
Huntsville, AL. cited by other .
Parker Hannifin Corporation, Parker Suparcase Process Hardens
Stainless Steel to Become More Resistant to Corrosion, News
Release, Parker Hannifin Corporation, Huntsville, AL. cited by
other .
Parker Hannifin Corporation, Engineering Report--Ferrule Design
Suparcase, Parker Suparcase Bulletin, 4230-B15.1, Parker Hannifin
Corporation, Huntsville, AL. cited by other .
Parker Hannifin Corporation, Parker Suparcase, A Proprietary
Process for the Hardening of Stainless Steel Ferrules, Parker
Suparcase Bulletin, Mar. 1993, 4230-B15.3, Parker Hannifin
Corporation, Huntsville, AL. cited by other .
Examination Report issued Aug. 4, 2006 from corresponding European
Patent Application Serial No. 02703345.5, 4 pgs. cited by other
.
Office action from Japanese Serial No. 2002-562904, dispatched Aug.
7, 2007, received on Nov. 9, 2007. cited by other .
Office action from Japanese Patent Application Serial No. 30722/05,
mailed Mar. 24, 2008, received on Mar. 31, 2008. cited by other
.
International Search Report and Written Opinion of
PCT/US2007/019025, mailed Apr. 29, 2008. cited by other .
International Search Report and Written Opinion from
PCT/US06/024776, mailed Jan. 19, 2007. cited by other .
Two pages, 4300 Catalog, Triple-Lok 37 degrees Flared Tube
Fittings, Parker Hannifin, Sep. 2000. cited by other .
International Search Report and Written Opinion from
PCT/US05/013758, mailed Aug. 12, 2005. cited by other .
Office action from Chinese Patent Application Serial No.
200580019992.1, dated Jan. 4, 2008. cited by other .
International Search Report and Written Opinion from
PCT/US06/041214, mailed Apr. 12, 2007, 12 pgs. cited by other .
International Search Report from PCT/US02/3430, mailed Nov. 6,
2002. cited by other .
Office action from U.S. Appl. No. 11/928,104 dated Jan. 15, 2009.
cited by other .
International Search Report and Written Opinion from PCT/US08/72072
dated Jan. 28, 2009. cited by other .
One page drawing, Drawing No. Standard 800 Series Space Collar
ASSY, (illustrated collar and fitting assembly offered for sale at
least as early as Feb. 5, 2000), Swagelok Company. cited by other
.
International Search Report from PCT/US07/83416 dated Apr. 21,
2008. cited by other .
Amendment from U.S. Appl. No. 11/112,800 dated Jan. 7, 2008. cited
by other .
Interview Summary from U.S. Appl. No. 11/112,800 dated Jul. 29,
2008. cited by other .
Amendment from U.S. Appl. No. 11/112,800 dated Aug. 1, 2008. cited
by other .
Office action from U.S. Appl. No. 11/112,800 dated Apr. 2, 2009.
cited by other.
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Primary Examiner: Bochna; David E
Attorney, Agent or Firm: Calfee, Halter & Griswold
LLP
Parent Case Text
RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 11/522,814, filed on Sep. 14, 2006 entitled "Tube Fitting with
Separable Tube Gripping Device" which is a continuation of U.S.
patent application Ser. No. 10/467,444, filed on Aug. 5, 2003, now
U.S. Pat. No. 7,108,288 entitled "Tube Fitting with Separable Tube
Gripping Ring" which claims priority to International Patent
Application Serial No. PCT/US02/03431, filed on Feb. 6, 2002
entitled "Tube Fitting with Separable Tube Gripping Ring" which
claims the benefit of U.S. Provisional patent application Ser. No.
60/266,735 filed on Feb. 6, 2001 entitled "Tube Fitting with
Integral Nut and Ferrule", and Ser. No. 60/329,943 filed on Oct.
17, 2002 entitled "Tube Fitting", the entire disclosures of which
are fully incorporated by reference.
Claims
The invention claimed is:
1. A tube fitting for a tube end, comprising: a first coupling
member; a second coupling member joined with said first coupling
member; a tube gripping device disposed between said first coupling
member and said second coupling member such that assembly of said
first coupling member with said second coupling member to a
pulled-up condition causes said tube gripping device to be
plastically deformed and swaged into the tube to grip and seal the
tube; wherein the first coupling member directly contacts an
internal surface of the second coupling member to provide an
indication of completed pull-up.
2. The tube fitting of claim 1 wherein the engagement of the first
coupling member with the internal surface of the second coupling
member provides a positive stop.
3. The tube fitting of claim 1 wherein the first coupling member
includes male threads that mate with female threads of the second
coupling member.
4. The tube fitting of claim 1 wherein the first coupling member
includes a camming surface that engages a nose portion of the tube
gripping device to cause the tube gripping device to grip and seal
the tube.
5. The tube fitting of claim 4 wherein a portion of the first
coupling member that is radially outward of the camming surface
engages the internal surface of the second coupling member to
provide an indication of completed pull-up.
6. The tube fitting of claim 1 wherein the second coupling member
includes a drive surface that engages a back end of the tube
gripping device.
7. The tube fitting of claim 6 wherein the internal surface of the
second coupling member that is engaged by the first fitting
component to provide an indication of completed pull-up is radially
outward of the drive surface.
8. The tube fitting of claim 1 wherein during pull-up a forward end
of said tube gripping device indents into an outer surface of the
tube end and said tube gripping device hinges radially inward so
that a portion of an interior wall of said tube gripping device is
radially compressed against the tube end.
9. The tube fitting of claim 1 wherein the tube gripping device is
attached to the second coupling member prior to pull-up.
10. The tube fitting of claim 9 wherein the tube gripping device
separates from the second coupling member during assembly of the
fitting to a pulled-up condition.
11. The tube fitting of claim 1 wherein the first coupling member
is a male coupling member and the second fitting component is a
female coupling member, wherein the male coupling member is joined
with said female coupling member such that said male coupling
member extends into said female coupling member.
12. The tube fitting of claim 11 wherein the male coupling member
includes a camming surface that engages a nose portion of the tube
gripping device to cause the tube gripping device to grip and seal
the tube and a portion of the male coupling member that is radially
outward of the camming surface engages the internal surface of the
female coupling member to provide an indication of completed
pull-up.
13. The tube fitting of claim 11 wherein the female coupling member
includes a drive surface that engages a back end of the tube
gripping ring and wherein the internal surface of the female
coupling member that is engaged by the male coupling member to
provide an indication of completed pull-up is radially outward of
the drive surface.
14. A method of assembling a tube fitting, comprising: joining a
first coupling member with a second coupling member such that a
tube gripping device is disposed between said first coupling member
and said second coupling member; engaging an internal surface of
the second coupling member with the first coupling member to
provide an indication of completed pull-up; wherein completed
pull-up of said first coupling member with said second coupling
member causes said tube gripping device to be plastically deformed
and swaged into the tube to grip and seal the tube.
15. The method of claim 14 wherein said indication of completed
pull-up is a positive stop.
16. The method of claim 14 wherein the first coupling member is
joined to the second coupling member with threads.
17. The method of claim 14 wherein during pull-up a forward end of
said tube gripping device indents into an outer surface of the tube
end and said tube gripping device hinges radially inward so that a
portion of an interior wall of said tube gripping device is
radially compressed against the tube end.
18. The method of claim 14 wherein said indication of completed
pull-up is provided by direct contact between the first coupling
member and said internal surface of the second coupling member.
19. A tube fitting for a tube end, comprising: a first coupling
member; a second coupling member joined with said first coupling
member; a tube gripping device disposed between said first coupling
member and said second coupling member such that assembly of said
first coupling member with said second coupling member to a
pulled-up condition causes said tube gripping device to be
plastically deformed to grip and seal the tube; wherein the first
coupling member directly contacts an internal surface of the second
coupling member to provide an indication of completed pull-up.
20. The tube fitting of claim 19 wherein the engagement of the
first coupling member with the internal surface of the second
coupling member provides a positive stop.
21. The tube fitting of claim 19 wherein the tube gripping device
is attached to the second coupling member prior to pull-up.
22. The tube fitting of claim 21 wherein the tube gripping device
separates from the second coupling member during assembly of the
fitting to a pulled-up condition.
23. The tube fitting of claim 19 wherein the tube gripping device
is a single ferrule.
24. A method of assembling a tube fitting, comprising: joining a
first coupling member with a second coupling member such that a
tube gripping device is disposed between said first coupling member
and said second coupling member; engaging an internal surface of
the second coupling member with the first coupling member to
provide an indication of completed pull-up; wherein completed
pull-up of said first coupling member with said second coupling
member causes said tube gripping device to be plastically deformed
to grip and seal the tube.
25. The method of claim 24 wherein said indication of completed
pull-up is a positive stop.
26. The method of claim 24 wherein said indication of completed
pull-up is provided by direct contact between the first coupling
member and said internal surface of the second coupling member.
27. The method of claim 24 wherein said tube gripping device is a
single ferrule.
Description
TECHNICAL FIELD OF THE INVENTION
The subject invention is generally directed to the art of tube
fittings.
BACKGROUND OF THE INVENTION
Tube fittings are used to join or connect a tube end to another
member, whether that other member be another tube end such as
through T-fittings and elbow fittings, for example, or a device
that needs to be in fluid communication with the tube end, such as
for example, a valve. As used herein the terms "tube" and "tubing"
are intended to include but not be limited to pipe as well. Any
tube fitting must accomplish two important functions within the
pressure, temperature and vibration criteria that the tube fitting
is designed to meet. First, the tube fitting must grip the tube end
so as to prevent loss of seal or tube blow out. Secondly, the tube
fitting must maintain a primary seal against leakage. The
requirement that a tube fitting accomplish these two functions has
been the driving factor in tube fitting design for decades. A
multitude of factors influence the design of a tube fitting to meet
a desired grip and seal performance criteria, but basic to any tube
fitting design will be: 1) the characteristics of the tubing that
the fitting must work with, including the material, outside
diameter and wall thickness; and 2) the tube grip and seal
performance level required of the tube fitting for its intended
applications. The goal is to design a tube fitting that reliably
achieves the desired tube grip and seal functions within whatever
cost constraints are imposed on the product by competing designs in
the marketplace.
A flareless tube fitting generally refers to a type of tube fitting
in which the tube end remains substantially tubular, in contrast to
a flared tube fitting in which the tube end is outwardly flared
over a fitting component. Flared tube ends are commonly encountered
in use with plastic tubing and plastic tube fittings. The present
invention is not primarily directed to plastic tubing or tube
fittings because such fittings have significantly different
challenges and material properties that affect the ability of the
fitting to both grip the tube and provide an adequate seal.
However, some of the aspects of the invention may apply to
non-metal tube fittings, particularly the separable tube gripping
element aspect.
Tube fittings that are intended for use with stainless steel and
other metal tubing, for example, are particularly challenging to
design in order to achieve the desired tube grip and seal
functions. This arises from the nature of stainless steel which, in
terms of typical commercially available tubing material, is a very
hard material, usually on the order of up to 200 Vickers. Stainless
steel and other metal tubing is also used for high pressure
applications in which the tubing wall thickness is substantial
(referred to in the art as "heavy walled" tubing). Heavy wall
tubing is difficult to grip because it is not only hard but it is
also not particularly ductile. Low ductility makes it more
difficult to deform the tubing plastically so as to achieve a
desired tube grip.
Tube fittings typically include an assembly of: 1) a tube gripping
device, often in the form of a ferrule or ferrules, or a gripping
ring-like structure, and 2) a pull-up mechanism for causing the
tube gripping device to be installed on a tube end so as to grip
the tube end and provide a seal against leakage. The term "pull-up"
simply refers to the operation of tightening the tube fitting
assembly so as to complete the assembly of the fitting onto the
tube end with the desired tube grip and seal.
Usually a tube fitting is first assembled in a "finger tight"
condition and then a wrench or other suitable tool is used to
tighten or "pull up" the fitting to its final initial and complete
assembled condition. The pull up mechanism most commonly used is a
threaded connection of a female threaded nut component and a male
threaded body component, with the tube gripping device being acted
upon by these two components as they are threaded and tightened
together. The body includes a tube end receiving bore with an
angled camming surface at the outer portion of that bore. The most
commonly used camming surfaces are frusto-conical such that the
term "camming angle" refers to the cone angle of the camming
surface relative to the tube end longitudinal axis or outer
surface. The tube end is axially inserted into the body bore and
extends past the frusto-conical camming surface. The gripping
device is slipped onto the tube end and the nut is partially
threaded onto the body to the finger tight position such that the
tube gripping device captured axially between the camming surface
and the nut. The nut typically includes an inward shoulder that
drives the tube gripping device into engagement with the angled
camming surface on the body as the nut and body components are
threadably tightened together. The angled camming surface imparts a
radial compression to the tube gripping device, forcing the tube
gripping device into a gripping engagement with the tube end. The
tube gripping device typically is to form a seal against the outer
surface of the tubing and also against the angled camming
surface.
The most commonly used tube gripping devices in stainless steel
tube fittings today (the most commonly used are ferrule-type tube
fittings) achieve tube grip by causing a front or nose portion of
the tube gripping device to bite into the tube end outer surface.
As used herein, the term "bite" refers to the plastic deformation
of the tube gripping device into the outer surface of the tube end
so as to plastically deform and indent the tubing with an almost
cutting-like action to create a generally radial shoulder or wall
at the front end of the tube gripping device. This "bite" thus
serves as a strong structural feature to prevent tube blow out at
high pressure, particularly for larger diameter tubing such as
1/2'' and higher.
Over the years there have been numerous tube fitting designs that
do not rely on a "bite" type action, but rather merely radially
compress the tube gripping device against the tubing outer surface,
some with the effect of indenting into the tubing without creating
a bite. These designs are not suitable for high pressure stainless
steel tube fittings. The most common commercially available
stainless steel tube fittings especially for high pressure
applications have historically been of two radically distinct
designs of the tube gripping device-single ferrule tube fittings
and two ferrule tube fittings.
A single ferrule tube fitting, as the name implies, uses a single
ferrule to accomplish both the tube grip and seal functions.
However, it is becoming increasingly recognized that these two
functions are at odds with each other when designing a tube fitting
that can meet a desired tube grip and seal performance criteria.
This is because the design criteria needed to assure that the tube
fitting achieves an adequate tube grip usually works against the
ability of the single ferrule to also provide an effective seal.
Consequently, although prior art single ferrule fittings can
achieve adequate tube grip in some cases, this tube grip
performance comes at the expense of having a less effective seal.
One result of this situation is that some single ferrule tube
fittings have been designed with additional components and
techniques to achieve an adequate seal. Less than optimum seal
performance is particularly noted in single ferrule fittings that
attempt to seal against gas, and especially high pressure gas.
Single ferrule tube fittings thus are usually more suited to lower
pressure liquid applications such as hydraulics, however, even in
such lower pressure applications single ferrule seal performance
remains less than desired.
For single ferrule tube fittings, the biting action is usually
associated with the single ferrule being designed to bow in a
radially outward direction from the tube wall in the central region
or mid-portion of the single ferrule body between the front and
back ends thereof. The front end of the ferrule is driven against
the angled camming surface of the body by the nut pushing against
the back end of the ferrule. The bowing action helps direct the
front end of the single ferrule into the tube end. The bowing
action is also used to cause the back end of the ferrule to
likewise engage and grip the tube end. This is accomplished usually
by provided an angled drive surface on the nut shoulder that
engages the back end of the single ferrule so as to radially
compress the back end of the ferrule into a gripping action on the
tube end. In some single ferrule designs, the back end of the
ferrule apparently is intended to bite into the tube end. This back
end tube grip is sometimes used with the single ferrule in order to
attempt to improve the tube fitting's performance under vibration
because the back end grip attempts to isolate down-tube vibration
from affecting the front end tube bite.
The use of a back end tube grip actually works against the effort
to grip the tube end at the front end of the single ferrule.
Ideally, the single ferrule should be completely in three
dimensional compression between the nut and the camming surface of
the body. Providing a back end grip actually places a counter
acting tension to the single ferrule that works against the front
end compression being used to provide the tube grip. Additionally,
the outward bowing action tends to work against the effort to grip
the tube at the front end of the single ferrule because, in order
to enable the outward bowing action, the single ferrule requires a
lessened mass that is adjacent the tube gripping "bite". The
outward bowing action radially displaces ferrule mass central to
the ferrule body away from the tube end. Consequently, an outwardly
bowed single ferrule fitting could be more susceptible to ferrule
collapse, loss of seal and possibly tube blow out at higher
pressures.
In order to achieve an adequate tube grip on stainless steel
tubing, single ferrule stainless steel tube fittings have
historically used a rather shallow camming angle of between ten and
twenty degrees. This range of angles is referred to herein as
"shallow" only as a term of convenience in that the angle is rather
small. The shallow camming angle has been used in single ferrule
fittings to obtain a mechanical advantage because the shallow angle
provides an axially elongated camming surface against which to
slide and radially compress the single ferrule front end to bite
into the tube end outer surface. Hard stainless steel tubing
material necessitated this elongated sliding camming action in
order to be able to get the single ferrule to create an adequate
bite for tube grip. Over the years, the single ferrule has been
through hardened or case hardened so as to be significantly harder
than the stainless steel tubing, however, the shallow camming angle
is still used today in such single ferrule fittings to obtain a
mechanical advantage from the ferrule sliding along the camming
surface to produce the "bite" so as to assure an adequate tube
grip. An example of a commercially available single ferrule tube
fitting that uses a case hardened ferrule and a shallow camming
angle of about twenty degrees is the CPI fitting line available
from Parker-Hannifin Corporation. Another example is the EO fitting
line available from Ermeto GmbH that uses a through hardened single
ferrule and a twelve degree camming angle.
In some single ferrule designs, a non-conical camming surface has
been tried whereby an attempt is made to simply press the ferrule
against the outer surface of the tube end, thereby not creating a
bite. The result in such cases however is a low grip or low
pressure only fitting that are not well suited to stainless steel
fittings.
The shallow camming angle and elongated camming surface and axial
movement needed to achieve an adequate tube grip with a single
ferrule fitting, however, compromises the ability of the single
ferrule to achieve the seal function, especially in extreme
environments and for sealing gas. This is because the front end of
the single ferrule attempts to make the seal against the axially
elongated camming surface. The radially outward bowing action
causes a larger portion of the outer surface of the front end of
the single ferrule to come into contact with the camming surface
against which it is being driven. The result necessarily is a
larger seal surface area between the outer surface of the single
ferrule and the camming surface. This enlarged seal area causes an
unwanted distribution of the sealing force between the single
ferrule and the camming surface, and also creates a larger area for
surface imperfections to allow leaks to occur. This is particularly
a metal to metal seal issue (as contrasted to non-metal to
non-metal seals: for example, in a plastic fitting it is usually
desirable to provide an enlarged seal contact area because the more
highly ductile plastic material can better form a seal between the
two surfaces.)
Because historically the single ferrule fitting has used a shallow
camming angle to achieve adequate tube grip, the less than optimum
seal function is either tolerated as a recognized limitation on the
application of the fitting, or additional features have been
designed into the single ferrule fitting, most notably attempts to
include one or more elastomeric seals with the single ferrule or
with which the single ferrule cooperates to provide a better seal
with stainless steel tubing. See, for example, U.S. Pat. Nos.
6,073,976 and 5,351,998. U.S. Pat. No. 6,073,976 illustrates a
typical example of a single "ferrule" (called a "cutting ring" in
the patent) fitting that attempts to solve the "seal" issue with
added elastomeric seal. The U.S. Pat. No. 5,351,998 describes the
benefits obtained by separating the tube grip and seal functions
into two separate components.
A commercially available and highly successful two ferrule fitting
used for tubing is commercially available from Swagelok Company,
Solon, Ohio and is described in U.S. Pat. Nos. 6,131,963 and
3,103,373 both of which are owned in common by the assignee of the
present invention, the entire disclosures of which are fully
incorporated herein by reference. In this two ferrule fitting, the
tube grip and seal functions also are separately achieved by the
use of two ferrules. The forward or front ferrule provides an
excellent seal even against gas, and the back or rear ferrule
provides an excellent tube grip.
The front ferrule achieves an excellent seal by camming against a
shallow camming surface angle such as twenty degrees. This is
because the front ferrule does not need to slide excessively on the
camming surface in order to achieve a tube grip function. Likewise,
the front ferrule is not case hardened because the primary purpose
of the front ferrule is to seal and is not to bite into the tube
end. Thus the relatively "softer" front ferrule achieves an
excellent seal, particularly against gas, even though the body
conical camming surface presents a camming angle of about twenty
degrees.
The back ferrule achieves the tube grip function in the above noted
two ferrule tube fitting. The back ferrule is case hardened to be
substantially harder than the tube end. The front end of the back
ferrule cams against a frusto-conical camming surface formed in the
back end of the front ferrule. The ostensible angle of this camming
surface is forty-five degrees, but due to the sliding movement of
the front ferrule, the effective camming angle is actually a
shallow angle of about fifteen to twenty degrees. Although the
effective camming angle for the back ferrule is shallow, the back
ferrule is not required to provide a primary seal (although it can
form secondary or backup seals). The back ferrule also does not
exhibit the undesired bowing action but rather grips the tube end
as a function of a radially inward hinging action. As used herein,
the term "hinging" refers to a controlled deformation of the
ferrule such that a central region or mid-portion of the ferrule
body undergoes an inwardly radial compression, as distinctly
contrasted to a bowing or radially outward displacement. Thus, the
effective shallow camming angle not only does not compromise the
fitting seal capability, it actually substantially enhances the
overall performance of the tube fitting especially for stainless
steel tubing.
By using separate ferrules for each to achieve primarily only one
of the key tube fitting functions, the two ferrule tube fitting
achieves tremendous tube grip and seal functions. This prior art
two ferrule tube fitting thus has enjoyed tremendous commercial
success especially in the art of stainless steel tubing in part due
to its performance characteristics such as high pressure rating on
the order of 15000 psi, wide temperature rating of cryogenic to
1200.degree. F. and in many applications a significant number of
remakes (a "remake" refers to the loosening and re-tightening of a
fitting after an initial pull-up).
U.S. Pat. No. 3,248,136 illustrates use of a single locking ring as
opposed to a ferrule, wherein the locking ring acts against a
surface having an angle that appears to be greater than twenty
degrees or more, but the ring does not appear to plastically deform
into the tubing but rather remains elastic so that the ring is
designed to retain its original shape after pull-up, both of which
are features that are unsuitable for stainless steel tube fittings
of the type considered herein. Japanese utility model publication
44-29659 illustrates a tightening ring that appears to be intended
to have a bowing effect and grip the tube at the front and back
ends. The fitting does not appear to be applicable to stainless
steel tubing as the tube is covered with a resin cover.
Attempts have been made to design tube fittings with a tube
gripping element that separates during pull-up to function as a
single element tube gripping device. Known designs place the
breakaway element on the male threaded component. Additionally, the
known designs either force the tube gripping element against a
shallow camming surface angle or do not attempt to create a tube
gripping bite into the tube wall. Thus the prior art designs suffer
from the same limitations as the prior art single ferrule tube
fitting designs.
Many applications and uses of the above-described two ferrule
SWAGELOK tube fitting do not require such high pressure,
temperature and remake performance characteristics. The present
invention is directed to a new fitting concept that can meet lower
performance characteristics without compromising overall fitting
integrity and performance.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, a new tube fitting
concept provides an indication of completed pull-up by engaging an
internal surface of one fitting component with another fitting
component. In one embodiment, a tube fitting has a first coupling
member and a second coupling member joined with the first coupling
member. A tube gripping device is disposed between the first
coupling member and the second coupling member such that assembly
of said first coupling member with said second coupling member to a
pulled-up condition causes the tube gripping device to grip and
seal the tube. The first coupling member engages an internal
surface of the second coupling member to provide an indication of
completed pull-up.
These and other aspects and advantages of the present invention
will be apparent to those skilled in the art from the following
description of the preferred embodiments in view of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may take physical form in certain parts and
arrangements of parts, preferred embodiments and a method of which
will be described in detail in this specification and illustrated
in the accompanying drawings which form a part hereof, and
wherein:
FIG. 1 illustrates in half longitudinal cross-section an exemplary
embodiment of a tube fitting in accordance with the invention in a
finger tight position;
FIG. 2 illustrates the embodiment of FIG. 1 in a partially pulled
up position;
FIG. 3 illustrates the embodiment of FIG. 1 in a completed initial
pulled up position; and
FIG. 4 illustrates another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In accordance then with one aspect of the invention, a tube fitting
is provided having a tube gripping device that initially is
integral with one of the coupling elements and upon pull-up
separates therefrom to function as a single ferrule fitting. In the
preferred embodiment, the tube gripping device or ferrule is
integrally formed with a female threaded nut and is attached
thereto by a frangible thin web portion that breaks as the ferrule
cams initially against a camming surface of the male threaded
component. As a single ferrule after separation, the ferrule acts
against the steep camming angle surface of a male threaded body.
The steep camming surface angle is particularly advantageous when
the hardness of the tube gripping device has a ratio of at least
about 3.3 times greater and preferably at least 4 times greater to
the hardness of the tubing material.
Although a number of aspects of the invention are described herein
as being incorporated into the exemplary embodiments, such
description should not be construed in a limiting sense. For any
particular application the various aspects of the invention may be
used as required in different combinations and sub-combinations
thereof. Furthermore, although the present disclosure describes
and/or illustrates a number of design choices and alternative
embodiments, such descriptions are not intended to be and should
not be construed as an exhaustive list of such choices and
alternatives. Those skilled in the art will readily appreciate and
understand additional alternatives and design choices that are
within the spirit and scope of the invention as set forth in the
appended claims.
Although the various embodiments are described herein with specific
reference to the fitting components being made of stainless steel,
and in particular 316 stainless steel, such description is intended
to be exemplary in nature and should not be construed in a limiting
sense. Those skilled in the art will readily appreciate that the
invention may be realized using any number of different types of
metal materials for the fitting components, as well as metal tubing
materials, including but not limited to 316, 316L, 304, 304L, any
austenitic or ferritic stainless steel, any duplex stainless steel,
any nickel alloy such as HASTALLOY, INCONEL, or MONEL, any
precipitation hardened stainless steel such as 17-4PH for example,
brass, copper alloys, any carbon or low alloy steel such as 1018
steel for example, and any leaded, re-phosphorized or
re-sulphurized steel such as 12L14 steel for example. An important
aspect of the choice of materials is that the tube gripping device
preferably should be case or through hardened to a ratio of at
least about 3.3 and preferably 4 or more times harder than the
hardest tubing material that the fitting will be used with.
Therefore, the tube gripping device need not be made of the same
material as the tubing itself. For example, as will be discussed
hereinbelow, the tube gripping device may be selected from the
stainless steel materials noted above, or other suitable materials
that can be case hardened, such as magnesium, titanium and
aluminum, to name some additional examples. Furthermore, the
frangible feature of the tube gripping ring and female threaded nut
may also be realized in non-metal tube fittings.
With reference to FIG. 1, the present invention contemplates a tube
fitting 50 in which there are only two discrete components prior to
assembly, namely a female threaded nut 52 and a male threaded body
54. The nut 52 is substantially different from the typical nut used
in a prior art ferrule type tube fittings. The body 54 may be the
similar in general design as a typical body used in prior fittings,
however, as will be explained further herein, it is preferred but
not necessary that the body 54 also be optimized for proper make-up
with the new nut 52. Additionally, the body 54 need not be a
discretely separate component but may be attached to or otherwise
integral to another part such as a valve body, manifold or other
components for example.
Note that in the drawings the fittings are illustrated in
longitudinal cross-section but only half of the section is
illustrated, it being understood that the other half is identical
and omitted for clarity and ease of illustration. In all of the
illustrations herein, various gaps and dimensions are somewhat
exaggerated for ease of illustration.
The body 54 is a generally cylindrical main body 56 that has an
integral extension or end 56a. The end extension 56a may be a hex
body, for example, or part of another component such as for example
a valve body as noted hereinabove. The main body 56 may be machined
from the same stock as the end extension 56a or may be otherwise
attached such as by welding or other suitable technique. The body
56 includes a first central longitudinal bore 58 that is
appropriately sized to closely and slideably receive a tube end 13.
The first bore 58 is somewhat larger in diameter than a coaxial
second bore 59 that extends through the end extension 56a of the
body 54. Of course, if the fitting 50 is a closed end connection,
the inner bore 59 would not be a through bore.
The tube end 13 preferably bottoms against a counterbore 60. The
body 56 is machined or otherwise formed with external male threads
62 that threadably mate with corresponding female threads 64 formed
or machined in the nut 52. It is contemplated that in order to
avoid inadvertent mixing of old and new style body and nut parts
with prior art fitting components, that the thread pitch on the nut
and body of the present invention may be substantially different
from the thread pitch values of prior art ferrule-type tube fitting
nuts and bodies. This will avoid interchange problems and also
allows for a course pitch that provides high axial stroke with
reduced nut rotation for complete pull-up. For example, a fitting
that incorporates the present invention may use course pitch
threads that provide sufficient axial displacement to achieve
proper pull-up in a half turn. A typical prior art fitting by
comparison is pulled-up with 11/4 to 11/2 turns. Nothing however
prevents the designer from making the thread pitch any value
suitable to a particular application, as there are other techniques
to avoid interchange issues. Therefore, the one-half turn for
pull-up is just one example of a variety of design choices
available.
The central body bore 58 is preferably although not necessarily
formed with a slight radially inward taper a relative to the
longitudinal axis X (FIG. 1) of the tube end 13 such that the
diameter of the bore 58 decreases radially in the axial direction
towards the counterbore 60. For example, this taper may be about
2.degree. to about 4.degree., although the selected angle is not
particularly critical. The bore 58 diameter at the counterbore
shoulder is just slightly less than the outer diameter of the tube
end 13. In this manner, the tube end 13 has a slight radial
interference fit of a few thousandths of an inch for example with
the bore 58. This interference between the bore 58 and the tube end
13 provides an anti-rotation action to help prevent the tube end 13
from rotating during pull-up. This also reduces residual torsion
stress that may be induced into the tube end due to rotation of the
tube gripping element (80) during pull-up. The tube end 13 does not
necessarily have to bottom completely against the counterbore
shoulder 60. This is because the interference fit helps provide a
good primary seal between the bore 58 and the tube end 13. The
interference fit also helps improve the tube grip by the tube
gripping element (80) by axially holding the tube end stationary
during pull-up so that the full axial displacement of the tube
gripping element (80) is used for proper deformation and tube grip
rather than any lost axial motion or movement of the tube end
during tightening. The taper of the bore 58 may extend gradually
along its entire axial length or a shorter axial portion adjacent
the counterbore 60.
The nut 52 includes a first central bore 70 having a first diameter
D1 relative to the longitudinal axis of the fitting 50. The nut 52
also includes a second bore 72 having a second diameter D2 relative
to the central longitudinal axis of the fitting 50. In this
embodiment, the diameter D2 is less than the diameter D1.
Furthermore, the diameter D2 is sized so that the bore 72 defines a
generally cylindrical wall that receives the tube end 13 (FIG. 2).
The first bore 70 terminates at a location that is axially spaced
from the nut back end 74 to form a trepan 75, such that the nut 52
includes a radially inwardly extending collar 76. The collar 76 is
generally defined by the back end wall 74 of the nut 52, the
smaller diameter bore 72 and the larger diameter bore 70.
In accordance with a significant aspect of the invention, the nut
52 includes a tube gripping device 80 that extends axially inwardly
in a somewhat cantilevered fashion from the collar 76. The tube
gripping device in this example is in the general form of a
gripping ring 80 and includes an inner bore 82 that defines a
substantially cylindrical wall that closely receives the tube end
13 (FIG. 2). The diameter D3 of the bore 82 may be the same as or
different from the diameter of the second nut bore 72. The
cylindrical wall that defines the gripping ring bore 82 extends
axially from a tapered front or nose portion 84 of the gripping
ring 80. The nose portion 84 includes an axially tapered outer
surface 86 that increases in the radial dimension towards the back
end of the ring 80. The tapered outer surface 86 extends from a
generally radial front end 85 of the gripping device 80. This
generally radial front end 85 joins to the inner cylindrical bore
82 at a preferably sharp corner 87. Alternatively, however, there
may be provided a circumferential recess or step or notch or other
geometry (not shown) in the front end of the ring 80 having a
diameter that is somewhat larger than the diameter D3 and axially
extending from the front end 85 towards the back end 74 of the nut
52.
The tapered surface 86 joins the front end 85 preferably by a
radius portion 89 and at its axial opposite end by a radius 86a to
a generally cylindrical portion 91, which in turn joins via a
radius 93 to the trepan 75.
It is noted at this point that the various geometry characteristics
of the tube gripping device 80 (such as, for example, the various
recesses, notches, tapered portions, radius portions and so on) are
selected so as to effect an appropriate radially inward hinging
action as will be further explained hereinafter. Accordingly, the
geometry of a tube gripping device 80 will be determined by the
characteristics of the material of the tubing such as hardness and
the fitting components, the dimensions of the tubing and the
required tube grip and seal performance needed for a particular
application. Therefore, the specific embodiments illustrated herein
are intended to be exemplary in nature and not limiting as to the
geometry of the tube gripping device. The above referenced patents
for the two ferrule fitting also illustrate additional geometry
variations to facilitate the hinging effect to obtain a desired
tube grip.
In accordance with another aspect of the invention, the tube
gripping device or ferrule 80 is attached to the female threaded
nut 52 by a thin frangible web portion 95. This web portion breaks
(as illustrated in FIG. 2) when the ferrule 80 cams initially
against a camming surface (88) during pull-up so that the tube
gripping device or ferrule becomes a separate piece and functions
with the nut and body in effect as a single ferrule fitting. The
separated ferrule 80 has a back end 150 that is axially driven by a
radially inwardly extending wall 152 of the nut 52 that serves as a
drive surface for driving the ferrule 80 forward against the
camming surface for completing an initial pull-up. The frangible
web portion 95 is preferably designed so that upon separation of
the device 80 from the nut 52, the surface 95a that is exposed
along the break line does not interfere with the drive surface 152
of the nut during further pull-up to complete the assembly. As used
herein, the terms "tube gripping device" and "ferrule" or "single
ferrule" are used interchangeably when referring to the device 80
after separation from the nut 52.
The ferrule 80 is machined with the frangible web 95 portion by
forming a radial groove 154 that is angled generally toward the
inside of the female threaded nut 52. This groove 154 forms the
back end 150 of the ferrule 80 and also the radial wall 152 of the
nut that drive the ferrule axially against the camming surface
after the ferrule 80 separates from the nut 52. Preferably but not
necessarily the wall 152 and the back end 150 are machined at an
angle of about 75.degree. or so relative to the tube bore axis X,
although this angle may be different depending on the particular
application. These surfaces 152 and 150 may be contoured to reduce
galling and torque if so required.
With reference to FIGS. 1, 2 and 3, the tapered nose portion 84
initially engages an axially tapered camming surface 88 that forms
an opening to the tube bore 58 in the main body 56. The tapered
camming surface 88 is a surface that joins the bore 58 wall to the
back end wall 90 of the body 54. This camming surface 88 is
characterized by a generally frusto-conical contour. However, the
shape of the surface 88 may be selected from other shapes depending
on the particular ring deformation and tube gripping
characteristics required for the fitting 50 in a specific
application.
Upon a completed pull-up, the back end 90 of the body 54 contacts
the trepan 75 which serves as a positive stop against over
tightening. Should remakes be desired, the back end 90 may be
axially spaced from the trepan 75 upon a completed first pull-up.
Proper pull-up in this case may be verified using a gap gauge or
other suitable technique, as is known.
The tube gripping ferrule 80 is shaped to effect several important
functions of the fitting 50. The ferrule 80 must, upon proper
pull-up, provide a fluid-tight primary seal against the tapered
camming surface 88. This seal may be a primary outer seal for the
tube fitting 50, or may be in effect a secondary or back-up seal to
any seal formed between the tube end 13 and the body 54, for
example along the bore wall 58 and/or the counterbore 60. The
separated ferrule 80 also will form a primary seal at the location
where the ferrule 80 bites into the outer surface of the tube end
13 in the area where the cylindrical bore 82 of the ferrule 80
engages the tube end outer surface. Again, this primary seal may in
effect be a back-up or secondary seal to any seal formed by the
tube end 13 against the body 54. In any event, the ferrule 80 must
form primary seals against the camming surface 88 and the outer
surface of the tube end 13. In addition, the ferrule 80 must
adequately grip the tube end 13 so as to maintain seal integrity
under pressure, temperature and vibration effects, and to prevent
the tube end from separating from the fitting under such
circumstances.
In order to achieve a fluid-tight seal and tube gripping action,
the ferrule 80 is designed to be plastically deformed and swaged
into the tube end upon completed pull-up, as illustrated in FIG. 3.
This result is achieved by designing the ferrule 80 to have a
hinging action whereby the tapered nose portion 84 is not only
driven axially forward as the nut 52 is threaded onto the body 54,
but also is radially displaced or driven into engagement with the
outer surface of the tube end 13 wall. The forward end 92 of the
nose portion 84 is thus compressed and embedded into the tubing
wall with a resultant stress riser or bite in the region designated
94 in FIG. 3. The front end bite 94 produces a generally radially
extending wall or shoulder 99 formed out of the plastically
deformed tube end material. The shoulder 99 engages the embedded
front end 92 of the gripping ring 80 to thus form an exceptionally
strong mechanical resistance to tube blow out at higher pressures.
The embedded front end 92 thus provides both an excellent seal and
a strong grip on the tube end 13. The ring 80 is further designed
to exhibit the aforementioned radially inward hinging action so as
to swage or collet the cylindrical wall 82 against the tube end at
a location axially adjacent or spaced from the stress riser bite 94
and generally designated with the numeral 96. This swaging and
collet effect substantially enhances the tube gripping function and
serves to isolate the embedded nose portion and bite 94 from the
effects of down tube vibration and also temperature changes.
Although the present invention is described herein in the various
embodiments as effecting an embedded nose portion and attendant
swaging action, those skilled in the art will appreciate that in
some applications such rigorous design criteria may not always be
required, particularly for fittings that will be exposed to
moderate temperature, vibration and pressure effects. Therefore,
the additional design aspects of the nut, body and gripping ring
set forth herein as preferred embodiments should therefore not be
construed in a limiting sense but rather as selectable enhancements
of the basic concepts of the invention to be used as required for
particular applications.
In order to achieve the desired swaging action and tube grip, the
ferrule 80 is designed to exhibit the hinging action that allows
the tapered nose portion 84 and the central or mid-portion (as at
the region of the cylindrical bore 82 or the region designated 94)
of the gripping ring 80 to be radially inwardly compressed as it
engages with the tapered camming mouth 88 of the body 56. This
hinging action is also used to provide a significant radial
displacement and compression of the cylindrical wall 82 to swage a
central or mid-portion of the ferrule 80 body onto the tube end 13
axially adjacent to the stress riser 94. In the embodiment of FIGS.
1-3, the hinging action is facilitated by providing a preferred
although not required radial inner circumferential notch 98 that is
axially positioned between the cylindrical portions 72 and 82. The
notch 98 is suitably shaped to permit the ferrule 80 to plastically
deform and collapse in a controlled manner so as to radially
compress the cylindrical wall 82 against the tube end with the
desired collet effect. The particular geometry of the gripping ring
80 will thus be designed so that as the nut 52 is further threaded
and tightened onto the body 54 after the ferrule 80 separates, the
ferrule 80 hinges and plastically deforms to grip the tube end and
to seal both against the tube end and the tapered camming mouth 88.
Standard design procedures such as Finite Element Analysis may be
used to optimize the geometry of the ring 80 based on variable
factors such as the tubing material, tubing hardness and wall
thickness, and required pressure, temperature and vibration
performance characteristics.
Proper deformation of the ferrule 80 may further be controlled by
selecting an appropriate contour for the tapered surface 88. This
surface engages the tapered nose of the ferrule 80 and therefore
will in part determine the timing and manner of how the ferrule 80
hinges, compresses and plastically deforms to properly embed the
nose portion to bite into the tubing and also provide the desired
collet or swaging action. Furthermore, the contour of the camming
surface 88 may be designed to achieve the desired seal between the
ferrule 80 nose portion and the tapered surface 88. This seal is
important to the overall performance of the fitting, as is the seal
provided between the ferrule 80 and the tube end 13.
The nut 52 with its integral tube gripping ferrule 80 may be
manufactured by standard machining operations, and will typically
include a trepan operation to form the outer contour of the ring
80. The other features of the nut 52 can be realized as well with
known machining operations. Preferably but not necessarily the nut
52 includes wrench flats 102 to permit the user to tighten the nut
52 onto the body 54. Those skilled in the art will readily
appreciate that use of the fitting 50 only requires relative
rotation between the nut 52 and the body 54, such that either
component or both may be rotated as required during a pull-up
operation.
We have found that it is highly desirable for the camming surface
88 to form a camming angle .theta. of about 35.degree.-60.degree.
relative to the longitudinal axis X of the fitting 50 and tube end
13. More preferably the angle .theta. of the camming surface 88
should be 40.degree.-50.degree., and most preferred the angle
.theta. should be about 45.degree.. This range of angles for the
camming surface 88 differs dramatically from commonly used metal
ferrule-type tube fitting designs. Commonly used tube fittings have
camming surface angles in the range of 10.degree.-25.degree., which
is a substantially shallower angle compared to the present
invention. The shallower camming angle is necessary in prior art
fittings to have the ferrule slide a greater axial distance along
the camming surface. This greater sliding action permits the tube
gripping device to be more gradually radially deformed into the
tube end to form a gripping action or bite on the tube. This is
especially the case for stainless steel tubing. Prior tube fittings
that included what might appear to be a steeper camming angle
actually either rely on a shallow portion of the camming surface or
do not produce a bite in the tubing, thereby limiting the pressure
resistance of the fitting. The shallow camming angle of the prior
art, however, compromises the ability of a single ferrule to form a
dependable seal. In sharp contrast, the present invention utilizes
a substantially steeper camming surface angle .theta., which
permits the gripping ring nose portion 84 in effect to be coined
into the camming surface 88 without substantial sliding action,
thereby forming an excellent seal.
In the exemplary embodiments herein, the nose portion 84 includes
the radius portion 89 that transitions to the outer tapered surface
86. This outer surface 86 tapers generally at an angle that is not
as steep as the angle of the camming surface 88. The tapered outer
surface 86 preferably tapers axially with an increasing radial
dimension towards the back end of the gripping ring 80. This
tapered outer portion 86 contacts the camming surface 88 with, in
effect, a generally narrow zone or line contact upon pull-up that
has high stress and material coining to allow the front end of the
gripping ring 80 to coin into the camming surface 88. Therefore,
the term "generally narrow line contact" is not intended to
preclude an area of contact between the outer tapered surface 86
and the camming surface 88, but rather more generally to the
concept of a localized contact zone near or at the innermost extent
of the camming surface 88 of high stress and material coining
between the outer tapered surface 86 and the camming surface 88. By
"coin" is simply meant that the gripping ring 80 achieves a good
metal to metal seal between the radius portion 89 and the camming
surface 88 by forming a generally narrow circumferential line
contact of metal burnished on metal to effect a gas tight primary
seal between the tapered surface 86 and the camming surface 88.
It is important to note that the use of a particular camming angle
is not dependent necessarily on the contour of the surface 88. In
other words, the angle of interest is the angle at which the front
end of the gripping ring 80 contacts the camming surface 88 to form
a seal thereat. Thus, the camming surface 88 may indeed be made
with a non-frusto-conical contour, but the seal is still formed by
the front end of the ferrule 80 contacting a steep angled surface
88. Additional compound angles or contours of the camming surface
88 may be used to better facilitate the hinging action and tube
bite achieved by the ferrule 80.
Whether the camming surface 88 is formed as a compound angled
surface with additional angled portions that are steeper or
shallower to facilitate the hinging action and bite of the gripping
ring 80 into the tube end 13, in accordance with this aspect of the
invention, the sealing portion of the front end of the gripping
ring 80 (in the exemplary embodiments the radius portion 89) forms
the primary seal on a steep angled portion of the camming surface
88, preferably a steep angled portion in the range of angle .theta.
of about 35.degree.-60.degree. relative to the longitudinal axis X
of the fitting 50 and tube end 13, more preferably the angle
.theta. of the camming surface 88 should be 40.degree.-50.degree.,
and most preferred the angle .theta. should be about 45 at the
location where the primary seal is to be formed. Preferably
although not necessarily this primary seal is effected by a
generally narrow line contact type engagement between the front end
of the gripping ring 80 and the camming surface 88.
The steeper camming surface angle has the additional benefit that
the nose or front portion of the tube gripping device 80 may be
formed with substantially more mass as compared to if the front
portion had to engage a shallower camming surface angle as in the
prior art single ferrule and gripping ring designs. This added
mass, along with the hinging action, tends to position a
substantially greater mass of material at or near the location of
the tube bite 94. This significantly strengthens the tube gripping
device in resisting pressure and also strengthens the collet effect
that isolates the bite from vibration and temperature effects, as
contrasted to prior art single ferrule or gripping ring designs.
The hinging action also results in the back end of the tube
gripping device (i.e. the end opposite the nose end 84) from
contacting the tube end, so that the entire tube gripping device is
in axial and radial compression.
In general, for a tube gripping device such as a ferrule to embed
into, bite and grip the tube end, the tube gripping device must be
harder than the tube end. This is especially so for thick wall
tubing. The greater axial movement of a ferrule in a shallow angle
camming mouth of the prior art allows a ferrule to embed into a
tube even when the ferrule is only moderately harder than the tube.
Under these circumstances if the tube gripping device 80 were only
moderately harder than the tube end, the device would be unable to
adequately grip the tube for a steep angle camming surface because
of the substantially shorter axial movement of the tube gripping
device during pull-up caused by the steeper camming angle. However,
in accordance with the present invention, by making the tube
gripping device significantly harder than the tubing, a steeper
angle camming surface may be used and is effective to cause the
tube gripping device to adequately bite into the tube end to grip
the tube.
The steeper camming angle .theta. of the present invention also
results in a much shorter distance of axial displacement of the
ferrule 80 during pull-up. Consequently, the nose portion 84 will
need to be radially deformed and compressed into the tube end 13
with a much shorter axial displacement or sliding movement. In
order to achieve the proper tube grip then, the ferrule 80 is
preferably case hardened to a hardness of at least about 3.3 times
harder than the tubing material. For example, if the tubing
material is stainless steel, it may exhibit a hardness of up to
about 200 Vickers. Therefore, in accordance with this aspect of the
invention, when the fitting 50 is used with such hard materials,
the tube gripping device should be hardened to a ratio of at least
about 3.3 times harder than the tubing. More preferred, the tube
gripping device should be hardened to a ratio of at least 4 times
harder than the tubing. Still further, the entire gripping ring 80
need not be case hardened, but rather only the nose portion 84 may
be selectively case hardened.
In accordance with this aspect of the invention, all or part of the
nut 52 and body 54 may be through hardened or case hardened to
increase the tube grip of the fitting 50 when used with harder
tubing materials such as stainless steel. Suitable case hardening
processes are fully described in U.S. Pat. Nos. 6,165,597 and
6,093,303 and copending patent application Ser. No. 09/494,093
filed on Jan. 28, 2000 for MODIFIED LOW TEMPERATURE CASE HARDENING
PROCESS, issued to the assignee of the present invention, the
entire disclosures of which are fully incorporated herein by
reference. These processes produce a hardness of the tube gripping
device of about 800 to 1000 Vickers or higher without compromising
the corrosion resistance of the fitting. Other case hardening
techniques however may be used as required. Case hardening of the
tube gripping ring 80 allows the ring 80 to adequately grip and
seal against tubing materials such as stainless steel including
duplex stainless steel. The above referenced case hardening patents
have an additional benefit of providing surfaces on the ring 80
that reduce or prevent galling between the ring 80 (which rotates
with the nut 52) and the tubing.
Various lubricants may also be used with the tube gripping ring 80
to reduce galling and residual torsion such as, for example, PTFE
greases, and greases containing molybdenum disulphide or tungsten
disulphide.
Case hardening techniques typically will result in the entire nut
52 and integral tube gripping ring 80 to be case hardened. When the
case hardening is performed on stainless steel, for example, as in
the above referenced patents or patent application, an adherent
oxide skin is formed. In another embodiment of the invention, a
solid lubricant may be applied to the threads of the stainless
steel nuts 52 to reduce friction and the hence pull-up torque
during tightening. Any solid lubricant can be used for this purpose
and many such solid lubricants are well known. A few examples are
graphite, molybdenum disulfide, tungsten disulfide and UHMWPE
(ultra high molecular weight polyethylene). These lubricants can be
used neat, i.e. not combined with another material, or mixed with
another material such as a resinous carrier or the like. In
addition, they can be used in essentially any solid form including
powders, granules and pastes.
Solid lubricants of this type are well known commercial products.
Examples include Dow Corning.RTM. 321 Dry Film Lubricant available
from Dow Corning Corporation of Midland, Mich. and Slickote.RTM.
Dry Lube 100 available from Trans Chem Coatings, of Monrovia,
Calif.
These lubricants can be applied by any standard method such as by
hand, by aerosol or air spraying or by automatic equipment. Any
coating thickness can be used which will provide lubricating
properties. Solid lubricant thickness exceeding standard class 2
thread clearances are usually not required. If appropriate, the
lubricant can also be heated to enhance its adhesion. For example,
some lubricants, especially those supplied in a resinous binder,
can be heated to effect cure of the binder. For example,
Slickote.RTM. Dry Lube 100 can be heated following manufacturer's
instructions to 300.degree. F. for 1 hour, for example.
In a particular embodiment of the invention, a dry lubricant as
described above is used on stainless steel nuts 52 which have been
subjected to low temperature carburization using carbon monoxide as
the carbon source. Stainless steel is stainless because of the
thin, coherent chromium oxide film which inherently forms when the
steel is exposed to air. Low temperature carburization of stainless
steel parts, such as those made from AISI 316 and 316L stainless
steel, usually leaves the part surfaces coated with a layer of
soot. Before use this soot is usually removed by washing. When
carbon monoxide is used as the carbon source in low temperature
carburization, not only does soot form but in addition a heavy
oxide film also forms. This heavy oxide film is considerably
different from the coherent chromium oxide film which makes
stainless steel stainless in that it is thicker and not coherent.
Therefore, this film is also removed before use to uncover the
part's carburized surface.
In accordance with this particular embodiment, this heavy oxide
film is not removed before application of the solid lubricant.
Rather, it is left on the carburized part surfaces, or at least the
portions of the carburized surfaces to be lubricated. In accordance
this particular embodiment, it has been found that the naturally
porous structure of this heavy oxide skin acts as an anchor for
binding the lubricant to the part surfaces. As a result, the
lubricant is more adherent than would otherwise be the case, and
hence is able to withstand repeated fitting remakes (i.e.,
loosening and re-tightening of the nut) without being removed.
FIG. 4 illustrates another embodiment of the invention in which all
elements are generally the same as the prior embodiment with one
variation. In the frangible web portion 95, a stress concentrating
notch 300 is formed therein. In this embodiment the stress
concentrating notch 300 is formed as a generally tight radius that
creates a thinner web of material 302 to promote a rapid clean
break of the ferrule 80 from the nut 52. The break thus occurs as a
result of a minimal span of rotation of the nut 52 shortly past
finger tight position. The shape of the break is also less ragged.
Other shapes of the notch 300 may be used as required including
elliptical, triangular and so on for example.
The invention has been described with reference to the preferred
embodiment. Clearly, modifications and alterations will occur to
others upon a reading and understanding of this specification. It
is intended to include all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *